difficulty in including patients

Breast cancer is the most common and most deadly malignant tumor in women. In the case of invasive breast cancer, cancer cells have invaded the tissues surrounding the tumor. Neoadjuvant chemotherapy (NAC) is a therapeutic strategy used in locally advanced invasive breast cancer, with the aim of reducing tumor size in order to increase the chances of breast preservation and reduce micrometastases. Accurate and reliable assessment of the locoregional response to NAC is essential because it allows for planning whether breast-conserving surgery is necessary.

Today, three minimally invasive imaging techniques are used to assess the response to NAC and the size of residual tumor: ultrasound, MRI, and PET. In routine practice, the choice of performing one, two, or three imaging techniques after NAC varies from one healthcare facility to another. Currently, there are no international recommendations, and decisions are made during multidisciplinary team meetings (MDTs), which include radiologists, oncologists, pathologists, and gynecologists.

A review of the literature has not established the superiority of one technique over another in determining the size of residual tumor after neonatal ablation (NAA). Several studies analyze each technique individually, but the methodologies differ. More recent studies compare ultrasound, MRI, and PET scans, but the small number of patients and the fact that some studies are retrospective make the results inconclusive. A prospective study conducted on a large number of patients, each examined using all three techniques after NAA and before surgery, would determine the most effective technique for assessing residual tumor size and, consequently, for deciding on the surgical procedure.

The main objective of this study is to compare the data collected by each of the three imaging techniques after neonatal ablation (breast ultrasound, MRI, and PET-CT) with the histological data of the tumor excised at the time of surgery.

Inclusion Criteria:

• Female patient
• Patient aged 18 years or older at the time of inclusion in the study.
• Patient with a diagnosis of advanced local invasive breast cancer, according to the TNM classification
• Patient scheduled for neoadjuvant chemotherapy after multidisciplinary tumor board meeting, and without contraindications after pre-treatment assessment
• Patient who has had a pre-cancer ultrasound, MRI, and/or PET scan
• Patient capable and willing to follow the protocol procedures according to the investigator
• Patient affiliated with or covered by a social security plan
• Patient who has given her free, informed, and explicit written consent

Exclusion Criteria:

• Patient with metastatic cancer
• Patient with another untreated associated cancer
• Patient already treated with CNA
• Patient who has been treated for cancer within the 5 years preceding their inclusion in the study
• Patient whose physical and/or psychological health is severely impaired, which, according to the investigator, may affect the participant's compliance with the study.
• Patient participating in another research study
• Patient on exclusion from another ongoing research study at the time of inclusion. Protected patient:

adult under guardianship, curatorship, or other legal protection, deprived of liberty by judicial or administrative decision.

• Pregnant, breastfeeding, or parturient woman.
• Patient hospitalized without consent.